The present invention relates generally to alternators, and more specifically, to a retainer assembly for supporting a bearing within an alternator housing.
Alternators have a rotor assembly with a shaft that is supported within a front and rear housing so that the rotor rotates with respect to a stator fixedly coupled within the housings. Typically, the rotor is positioned within the housing by a front bearing that couples to the front housing and a rear bearing that couples to the rear housing. Commonly, the front and rear bearings are press fit together so that the outer diameter of the bearing is held in place rotationally.
The housings of the alternator are commonly made from aluminum. The outer diameter of the bearings is formed of steel. Aluminum and steel expand at different rates when heated. Therefore, a press fit steel bearing into an aluminum housing is not sufficient to hold the bearing rotationally since the hole in the housing grows faster than the outer diameter of the bearing. One solution for this problem include incorporating plastic bands on the outer diameter of the bearing then press fitting the bearing into the aluminum housing. Another method for securing a bearing within a housing is adding a plastic sleeve between the housing and the bearing. Another method is to press the bearing into a steel sleeve that is attached to the aluminum housing. Each of these methods adds expense due to the additional components.
The rotor assembly has a field coil and claw pole fingers that generate a magnetic field. The field coil is energized by a pair of slip rings that are electrically connected to each end of the coil. The slip rings are commonly located on the outside of the housing. A brush holder is positioned on the outside of the housing whereby electrical contact between the brushes within the brush holder and the slip rings provide electrical power to the field coil.
Brushes are sensitive to contaminants. Commonly, a wall or extension may extend from the housing to partially protect the brushes. In such cases, however, the brushes are not completely sealed from the environment and therefore may become contaminated. Also, as the brush wears, carbon dust from the brushes may enter the housing and contaminate the stator and rotor and could potentially cause short circuits therein. Known brush protection does not address carbon dust contamination into consideration.
One consideration in alternator design is the overall size of the alternator package. Engine compartment space continues to be more compact and therefore reducing the size of the components including the alternator is desirable.
It is therefore desirable to provide an integral bearing assembly/brush retainer that prevents outside contamination of the brushes as well as prevents brush dust from contaminating the alternator in a small package.
It is therefore one object of the invention to provide an integral brush holder and bearing assembly that secures the brush assembly to the bearing assembly and is easy to assemble into the alternator package.
In one aspect of the invention, a bearing retainer assembly has a bearing retainer housing having a generally cup-shaped end portion and a coupling portion that couples the housing to the cover. A bearing retainer liner is positioned within the cup-shaped end portion and is sized to receive the bearing.
One feature of the invention is that the liner may be integrally molded with the retainer housing. A plurality of tabs formed in the end surface of the liner may be used to help retain the liner within the housing.
The bearing retainer assembly may also have a brush holder retaining portion that has a pair of receiving channels therein. A brush holder housing having retention flanges extending therefrom is sized to be received within the receiving channels. During the assembly process, brushes may be loaded into the brush holder housing. Then, the brush holder retention flanges are inserted within the receiving channels. A cap portion is sized to couple to the brush holder retaining portion and is sized to retain the brush holder together with the bearing retainer housing.
One advantage of the invention is that the bearing retainer assembly is a compact size. Another advantage of the invention is that both axial and rotational movement of the rotor is prevented with the bearing retainer assembly.
Other objects and features of the present invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and appended claims.